The present invention relates to a throttle valve connection fitting or piece for an internal combustion engine. Such fittings may be made integral or modular depending upon application. The throttle valve may comprise a butterfly valve. Generally, such fittings include an internal through-opening with the valve pivotably mounted therein. The valve may be made to pivot between an open and shut position which, respectively, facilitate and halt flow through the opening. To facilitate the pivoting, the valve may be mounted on a pivot axis which would run transverse to a longitudinal axis of the opening.
In the closed position, the ends of the valve contact the interior walls of the opening thereby preventing through passage. In the closed position, the valve is inclined by a certain setting angle relative to the longitudinal axis and bearing, at a bearing region, with its radially encircling edge against the inner wall of the opening. The opening includes a cylindrical design at least in the bearing region of the valve.
In order to obtain precisely definable throughflow cross sections in the region of the valve, in particular close to the closed position, and in order to ensure satisfactory closing in the closed position, the throughflow opening of the valve connection piece is designed to be cylindrical in the bearing region of the valve. Since the valve, in its closed position, is inclined relative to the longitudinal axis of the throughflow opening by the setting angle, this region of cylindrical cross section extends over the entire length which is covered by the valve located in the closed position. This length of about 7 to 10 mm is too large for it to be capable of being produced with a single cylindrical core, since no demolding is then possible without damage to the cylindrical wall by scores.
In order to achieve damage-free demolding, two cores are used, whose end regions facing one another are cylindrical and come to bear against one another for the die-casting/injection-molding operation.
However, this results in a forming ridge at this bearing point between the two cores and also in an axial offset due to tolerances, which necessitates rework after the demolding, since otherwise the valve may jam in its closed position.